Title of Invention

A NON-INCENDIVE, WATER-IN-OIL EMULSION EXPLOSIVE COMPOSITION AND A PROCESS FOR PREPARING SUCH COMPOSITION

Abstract

A non-incendive, water-in-oil emulsion explosive composition which comprises an aqueous solution of one or more inorganic oxidiser salts, a fuel phase and 5 to 50% by weight of the total composition of one or more solid dopants, wherein said solid dopant(s) at least include a coolant selected from one or more of alkali metal and alkaline earth metal salts and ammonium chloride and said non-incendive water-in-oil emulsion explosive composition includes a flame quencher selected from ammonium, alkali metal, alkaline earth metal or transition metal salts of phosphoric acid.

Full Text

The present invention relates to water-in-oil emulsion explosive compositions that can be used at P-5 permitted explosives in underground coal mines of Degree III gassiness. More particularly, the present invention relates to a non-incendive, water-in-oil emulsion explosive composition and a process for preparing such composition. P-5 type of explosives are commonly used in underground coal mines of high gassiness. These explosives are also specifically approved for Blasting of solid application in Degree I & II mines. Currently NG type of explosives are used. However, these conventional explosives suffer from several the inherent drawbacks. These include the physiological effects of use of NG explosives as well as high post detonation toxic fumes and deflagration characteristics. In an attempt to overcome some of the above-mentioned drawbacks watergel explosives have been used with a limited success. Watergel explosives show reduced post detonation toxic fumes and low tendency to deflagrate. However, performance of the watergels have generally been unreliable. P-5 emulsion explosives are expected to overcome these problems while affording the advantages of very low post detonation toxic fumes. They are also non-deflagrating. The design of P-5 explosives is an art in itself because of conflicting requirements with respect to statutory approvals and performance. In order to be able to pass the stringent gallery tests it -: 2 : - is essential to dope the explosive with large quantities of inerts. However, doping explosives with inerts, more often than not adversely affects the sensitivity of the explosive as well as its performance. Therefore, an optimum balance has to be arrived at in making such experiments. Water-in-oil emulsion explosives which can be used under P1&P3 conditions i.e. Degree I and Degree II gassiness mines are disclosed in prior art. These explosives require coolants since hot explosive gases which are released tend to ignite methane/air gas mixtures in underground mines. Such coolants have normally been water and salt US P5017251 defines use of salt for P1 type of explosives. Similarly prior art literature also reports very high doping of salt and use of glass microballoons at high loading to achieve the desired sensitivity (Patent No. ZA 043516 US 6017261M AU 0067072M AU 8656181 US 4976793M CN 1031363) . The use of such high loading of GMB's is an economically unviable proposition. The basic object of the present invention is therefore, to provide a P-5 emulsion explosive which overcomes the drawbacks and disadvantages of prior art compositions. A still more specific object of the invention is to provide an economically viable chemically gassed explosive P-5 emulsion type composition. A further object of the invention is to provide a P-5 composition in which in addition to use of water and salts of alkali metals as coolants, the need for a flame quencher has been unequivocally -: 3 : - established. Yet another object of the invention is to provide a P-5 emulsion explosive composition which is sensitive to detonation in 32 mm diameter using commercially available blasting caps which are approved for use in underground coal mines. Accordingly, there is provided a non-incendive, water-in-oil emulsion explosive composition which comprises an aqueous solution of one or more inorganic oxidiser salts, a fuel phase and 5 to 50% by weight of the total composition of one or more solid dopants, wherein said solid dopant(s) at least include a coolant selected from one or more of alkali metal and alkaline earth metal salts and ammonium chloride and said non-incendive water-in-oil emulsion explosive composition includes a flame quencher selected from ammonium, alkali metal, alkaline earth metal or transition metal salts of phosphoric acid. Accordingly, there is also provided a process for the manufacture of a non-incendive water-in-oil emulsion explosive composition as claimed in claim 1 which comprises forming an aqueous solution of said one or more inorganic oxidiser salts, combining said aqueous solution with the fuel phase, adding to said mixture the one or more solid dopant coolants, adding the flame quencher, and emulsifying said mixture to obtain said emulsion explosive composition. The composition of the present invention is neither a product of chemical reaction nor a mere admixture resulting in the aggregation of the properties of the components thereof and is in fact a synergistic mixture having improved and unexpected properties. -4- Accordingly, the present invention provides a non-incendive, water-in-oil emulsion explosive composition which comprises from 50 to 80% by weight of an aqueous solution of inorganic oxidiser salts such as herein described, from 3 to 60% by weight of a fuel phase and from 5 to 50% by weight of one or more solid dopants of the kind such as herein described. The inorganic oxidiser salts, which in the aqueous solution constitute the discontinuous phase of the P-5 emulsion explosive compositions of the present invention are selected from ammonium nitrate, alkali metal nitrates such as sodium nitrate or potassium nitrate. In addition, a chemical sensitiser such as perchlorate salts sodium, potassium or ammonium may be included, the preferred one being sodium perchlorate. The composition will also include a. flame quencher. The flame quencher is selected from the preferred salts of phosphoric acid such as mono, disodium ammonium and also hexametaphosphates, the most preferred ones being ammonium salts. The flame quenchers of the present invention may be used either in the oxidiser solution phase of the P-5 emulsion formulations" or as one of the components of solid dopants or both. -5- The water content of the aqueous solution of the inorganic oxidiser salt preferably comprises from 5 to 16% by weight based on the total weight of the explosive composition. The fuel phase comprises a mixture of straight chain and branched chain waxy materials which are commonly referred to as microcrystalline and paraffin waxes, emulsifiers and fuel comprising paraffin oil either alone or in combination with a residue from petroleum crude of low sulphur content which is commercially known as LSHS. This fuel is known to make the bilayers more flexible when subjected to stress and thus help reduce the shear sensitivity of the doped emulsions. The emulsifiers employed in the composition of the present invention impart a high degree of stability to the composition especially, in view of the high quantity of dopants. These emulsifiers which are employed with respect to other ingredients in predetermined molar ratios include the particularly preferred condensation product(s) of maleinised polyisobutylene based surface active agent(s) and alkanot amines and are manufactured under the code name E-475/E-476. This is present in an amount ranging from 0.5 to 3.0%, preferably, in the region of 1.0 to 3.0%. Other emulsifiers include polymers prepared by the condensation of long chain aliphatic carboxylic acids with polyethylene glycol of molecular weight between 400 and 3000, esters of sorbitol with long chain fatty acids such as sorbitan monooleate (SMO), sorbitan trioleate (STO) or sorbitan sesquioleate (SSO), phospholipids such as soyalecithin (SL) or oxazoline or imidazoline derivatives -6- thereof, lanolin, a steroidal product obtained from wool fat or phosphoric acid esters and also other paraffinic fuel-compatible surfactants available under different brand names. The improved emulsion explosive composition of the present invention may include - in addition to the unique highly branched paraffinic hydrocarbon fuel referred to above - combinations of one or more of other conventional carbonaceous fuels depending on consistency of the final emulsion compositions desired. By way of examples, these additional carbonaceous fuels include microcrystalline wax, slack wax, paraffin wax, montan wax, whale wax, bees wax, agro wax, ozokerite, diesel oil, paraffin oil, tall oil and other hydrocarbon fuels containing paraffinic hydrocarbons, aromatic hydrocarbons, olefinic hydrocarbons or nitrocarbons. The flame quencher used in the P-5 emulsion composition of the present invention is selected from dibasic salts of phosphoric acid such as sodium, ammonium and potassium, preferably ammonium salts and/or hexametaphosphate salts. These salts can be incorporated either in the aqueous solution or added as a solid dopant or as a combination of both. These are present in an amount ranging from 0.1 to 10.0%, preferably, in the range of 0.5 to 8.0% and most preferably, in the range of 1.0-6.0%. In addition to the flame quencher salt{s) of the present invention, the other flame quencher salts added as solid dopants solid dopants to confer non-incendivity to the water-in-oil emulsion explosive when subjected to gallery testing as per IS:6609 (Part 11/Sec. 2} -1974 include salts of alkali metals, preferably, chlorides of -7- sodium or potassium. These are present in an amount in the range from 5 to 50%, preferably, in the region 10-35%. In addition, the flame quencher salts as defined above can also be included as solid dopants. The present invention also provides a process for the manufacture of a non-incendive water-in-oil emulsion explosive composition which comprises forming in any known manner an aqueous solution of one or more inorganic oxidiser salts such as herein described, combining in any known manner said aqueous solution with a blend of at least one fuel, adding to said mixture, one or more solid dopants of the kind such as herein described and emulsifying in any known manner, said mixture, to obtain said emulsion explosive composition in which said aqueous solution of inorganic oxidiser salt constitutes from 50 to 80% by weight, said fuel phase constitutes 3 to 60% by weight and said solid dopants constitute from 5 to 50% by weight. Preferably, the aqueous solution of the oxidiser salts is maintained at a temperature of 60°C to 100°C while the fuel-emulsifier blend is kept at a temperature of 70°C to 90°C before being fed for emulsification to an emulsification apparatus. This apparatus can be either a motionless static mixer or rotary emulsifying equipment. The flame quenching agent is incorporated into said aqueous inorganic oxidiser salts solution prior to combination thereof with said blend & emulsification of the mixture -8- In accordance with yet a further feature of the invention, after emulsification, a chemical gassing agent such as herein described is incorporated into the emulsion for controlling its density. More preferably the gassing agent is incorporated into said emulsion by shearing action in order to disperse it properly therein and facilitate interaction between the gassing agent and the oxidizer salts present in the micro droplets. If required, the resulting emulsion can be further refined in any known manner. Depending upon the purpose and the end use of the products, the emulsions can be cooled to a desired temperature lower than the temperature of manufacture. Finally, the emulsion explosives are cartridged in suitable packages of desired diameter. It must be borne in mind that the embodiment described is merely illustrative of the present invention which is not limited to the specific examples mentioned herein. The invention will now be described, by way of non-limiting illustrative examples. -9- Example X Ingredient x by weight Ammonium Nitrate 45.4 Sodium Nitrate 7.7 Sodium Perchlorate (100%) 5.6 Water 7.7 PIBSA Surfactant 2.1 Sorbitan Mono Oleate 0.14 Paraffinic Oil 2.24 Rubber Latex 0.07 Sodium Nitrite 0.10 Sodium Chloride 30.00 Ammonium Nitrate 42.6 Sodium Nitrate 7.0 Sodium Perchlorate (100%) 5.6 Diammonium hydrogen phosphate 2.8 Water 7.7 PIBSA Surfactant 2.1 Sorbiton Mono Oleate 0.14 Paraffinic Oil 1.89 Rubber Latex 0.07 Sodium Nitrite 0.10 Sodium Chloride 30.00 -10- There were subjected to incendivity tests as applicable to Group P5 permitted explosives as per IS:6609 (Part II/Sec. 2) - 1974 and the results are given below : No. of Ignitions Example I Example II shots allowed 1 ) Inverse initiation 20 shots Nil 2 Nil to methane/air under of 565 g cut-off condition 2) Direct initiation 5 shots of Nil Not done Nil into methane/air 1030 g 3) Inverse initiation 5 shots of Nil Not done Nil into coal dust 565 g The above examples clearly delineate the role of salts of phosphoric acid in conferring non-incendive character to a formulation. -11- WE CLAIM : 1. A non-incendive, water-in-oil emulsion explosive composition which comprises an aqueous solution of one or more inorganic oxidiser salts, a fuel phase and 5 to 50% by weight of the total composition of one or more solid dopants, wherein said solid dopant(s) at least include a coolant selected from one or more of alkali metal and alkaline earth metal salts and ammonium chloride and said non-incendive water-in-oil emulsion explosive composition includes a flame quencher selected from ammonium, alkali metal, alkaline earth metal or transition metal salts of phosphoric acid. 2. A non-incendive water-in-oil emulsion explosive composition as claimed in claim 1 wherein the flame quencher is a dibasic salt of phosphoric acid. 3. A non-incendive water-in-oil emulsion explosive composition as claimed in claim 2 wherein the flame quencher is a hexametaphosphate salt. 4. A non-incendive, water-in-oil emulsion explosive composition as claimed in any preceding claim wherein the flame quencher is present in an amount of 0.1 to 10% by weight. 5. A non-incendive, water-in-oil emulsion explosive composition as claimed in any preceding claim wherein the flame quencher is present at least partly in the aqueous solution of inorganic oxidiser salt(s). -12- 6. A non-incendive, Water-in-oil emulsion explosive composition as claimed in any preceding claim wherein the flame quencher is present at least partly as one or more of the solid dopants. 7. A non-incendive, water-in-oil emulsion explosive composition as claimed in any preceding claim wherein said coolant is selected from one or more of chlorides of sodium, potassium and ammonium. 8. A non-incendive, water-in-oil emulsion explosive composition as claimed in any preceding claim wherein said one or more solid dopants are present in an amount of 10 to 40% by weight, preferably 20 to 35% by weight of the composition. 9. A non-incendive, water-in-oil emulsion explosive composition as claimed in any preceding claim wherein said one or more oxidiser salts are selected from ammonium nitrate, alkali metal nitrates and perchlorate salts of sodium, potassium and ammonium. 10. A non-incendive, water-in-oil emulsion explosive composition as claimed in any preceding claim wherein the water content of said composition is in the range of 5 to 16% by weight. 11. A non-incendive, water-in-oil emulsion explosive composition as claimed in any preceding claim wherein said fuel phase comprises one or more members selected from the group consisting of carbonaceous fuels such as low sulphur heavy stock, micro crystalline wax, slack wax, paraffin wax, montan wax, whale wax, bees wax, agro wax, ozokerite, diesel oil, paraffin oil, tall oil and other hydrocarbon fuels containing paraffinic hydrocarbons, aromatic hydrocarbons, olefinic hydrocarbons or nitrocarbons. -13- 12. A non-incendive water-in-oil emulsion explosive composition as claimed in any preceding claim wherein said fuel phase contains at least one fuel comprising highly branched paraffinic hydrocarbon and/or their isomers having from 14 to 40 carbon atoms. 13. A non-incendive water-in-oil emulsion explosive composition as claimed in any preceding claim wherein said fuel phase comprises an emulsifier selected from one or more of condensation products of polyisobutylene surface active agent and alkano amines and long chain aliphatic carboxylic acids with polyethylene glycol of molecular weight between 400 and 3000, esters of sorbitol with long chain fatty acids such as sorbitan monooleate (SMO), sorbitan trioleate (STO) or sorbitan sesquioleate (SSO), phospholipids such as soyalecithin (SL) or oxazoline or imidazoline derivatives thereof, lanolin, a steroidal product obtained from wool fat or phosphoric acid esters and also other paraffinic fuel compatible surfactants. 14. A non-incendive water-in-oil emulsion explosive composition substantially as herein described with reference to Example II. 15. A process for the manufacture of a non-incendive water-in-oil emulsion explosive composition as claimed in claim 1 which comprises forming an aqueous solution of said one or more inorganic oxidiser salts, combining said aqueous solution with the fuel phase, adding to said mixture the one or more solid dopant coolants, adding the flame quencher, and emulsifying said mixture to obtain said emulsion explosive composition. 16. A process as claimed in claim 15, wherein at least some of the flame quencher is added to the aqueous solution. -14- 17. A process as claimed in claim 15 or claim 16 wherein at least some of the flame quencher is added to the mixture as solid dopant. 18. A process as claimed in any one of claims 15 to 17 wherein said emulsification is carried out in the presence of a gassing agent and/or density reducing agent. 19. A non-incendive, water-in-oil emulsion explosive composition substantially as hereinbefore described with reference to the foregoing examples. 20. A process for the manufacture of a non-incendive water-in-oil emulsion explosive composition substantially as hereinbefore described with reference to the foregoing examples. 20. Dated this 10th day of February, 1997. -15- A non-incendive, water-in-oil emulsion explosive composition which comprises an aqueous solution of one or more inorganic oxidiser salts, a fuel phase and 5 to 50% by weight of the total composition of one or more solid dopants, wherein said solid dopant(s) at least include a coolant selected from one or more of alkali metal and alkaline earth metal salts and ammonium chloride and said non-incendive water-in-oil emulsion explosive composition includes a flame quencher selected from ammonium, alkali metal, alkaline earth metal or transition metal salts of phosphoric acid.

Documents:

00225-cal-1997-abstract.pdf

00225-cal-1997-assignment.pdf

00225-cal-1997-claims.pdf

00225-cal-1997-correspondence.pdf

00225-cal-1997-description(complete).pdf

00225-cal-1997-form-1.pdf

00225-cal-1997-form-13.pdf

00225-cal-1997-form-2.pdf

00225-cal-1997-form-26.pdf

00225-cal-1997-form-3.pdf

00225-cal-1997-form-5.pdf

00225-cal-1997-pa.pdf

225-CAL-1997-FORM-27.pdf

225-cal-1997-granted-abstract.pdf

225-cal-1997-granted-assignment.pdf

225-cal-1997-granted-claims.pdf

225-cal-1997-granted-correspondence.pdf

225-cal-1997-granted-description (complete).pdf

225-cal-1997-granted-examination report.pdf

225-cal-1997-granted-form 1.pdf

225-cal-1997-granted-form 13.pdf

225-cal-1997-granted-form 2.pdf

225-cal-1997-granted-form 26.pdf

225-cal-1997-granted-form 3.pdf

225-cal-1997-granted-form 6.pdf

225-cal-1997-granted-letter patent.pdf

225-cal-1997-granted-pa.pdf

225-cal-1997-granted-reply to examination report.pdf

225-cal-1997-granted-specification.pdf